The present invention relates generally to thermal sensors. More particularly, the present invention relates to a thermal wake-up circuit.
Circuits and electronic devices are being used for an increasing variety of applications. Some applications may subject the circuits to adverse environmental conditions. One environmental condition often found to affect the operation of a circuit is the temperature.
The circuit can be affected by internal heating of the components or by ambient temperature. Events that occur on the circuit may push excess current through the circuit or device. The ambient temperature can be a result of a number of different sources of heat. The heating of nearby components or connected devices may cause an increase in the temperature associated with a circuit. In addition, changes in ambient temperature resulting from where the circuit is placed or stored may result in adverse circuit operation.
Most electronic circuit are subject to temperature specifications. The temperature specification usually defines a range of temperature recommended for optimal circuit performance. Exceeding the upper limit or lower limit of the temperature range may cause a degradation in circuit operation.
Thermal sensors are often utilized to monitor the temperature associated with a particular circuit. Protection circuitry may be utilized to prevent damage to the circuit as a result of temperature variations.
The present invention relates generally to thermal sensors. More particularly, the present invention relates to a thermal wake-up circuit and a thermal sensor that are utilized by another circuit. The thermal wake-up circuit provides improved power efficiency by activating temperature sensors as the temperature of the other circuit approaches a level associated with each temperature sensor. The thermal wake-up circuit activates a thermal sensor when the temperature of the other circuit exceeds a first threshold level. Once activated, the thermal sensor monitors when the temperature of the other circuit exceeds a second threshold level. The thermal sensor activates protection circuitry or deactivates the other circuit, preventing adverse circuit operation caused by the temperature increase, when the temperature of the other circuit exceeds the second threshold level. In another embodiment, additional thermal sensors may be used. Each of the additional thermal sensors are activated when the temperature exceeds the first threshold level. Each of the additional thermal sensors monitors the temperature of the other circuit. Each of the additional thermal sensors has an associated threshold level, and may be used to activate other circuitry or deactivate the other circuit according to each associated threshold level.
Stated briefly, an apparatus and method is directed to a thermal wake-up circuit and a thermal sensor that are utilized by another circuit. The thermal wake-up circuit monitors a temperature associated with the other circuit. The thermal sensor is activated by the thermal wake-up circuit when the temperature exceeds a first threshold level. The thermal sensor is deactivated by the thermal wake-up circuit when the temperature is below the first threshold level. In one embodiment, addition thermal sensors may be activated and deactivated by the thermal wake-up circuit. The thermal sensor and additional thermal sensors may be used to activate protection circuitry or to shut down the other circuit. Power consumption by the thermal sensor is minimized by maintaining the thermal sensor inactive until activated by the thermal wake-up circuit.